1. Field of the Invention
This invention relates to asphalt emulsions, products made from asphalt emulsions, in particular to fibrous mats useful for making building materials, and processes for manufacturing the fibrous mats. The fibrous mats made with the asphalt emulsions of the invention allow for the preparation of lighter than traditional fibrous mats while providing excellent tear resistance and tensile strength.
2. Description of the Prior Art
High strength, uniform thin sheets of glass fibers are important in the building materials industry. These products are typically used in roofing shingles.
In the past, asphalt roofing shingles have been constructed of an organic rag felt impregnated and coated with asphalt or other bituminous substance. However, asphalt-impregnated rag felt mats are difficult to manufacture in large quantities and are costly.
Glass fiber mats were developed in an attempt to improve upon the more-expensive and difficult to process asphalt-impregnated rag felt mats. There are numerous glass mats described in the art that are formed commercially of glass fibers. These mats include glass fibers held together by binder materials. A common binder material used in glass mats is urea-formaldehyde, which may be deemed undesirable if toxic formaldehyde is released from the mats, when they are stored.
Efforts have been made to improve glass mat strength. These efforts have focused on modifying the binders used in making fiber mats, the processes employed in manufacturing the glass mats and/or the fibrous composition of the mats.
U.S. Pat. No. 2,731,066 describes a glass fiber mat formed from a dry process. The mat includes chopped glass fibers arranged in a haphazard pattern reinforced with continuous strands, yarns or slivers bound together with a bonding agent. Suitable bonding agents disclosed in U.S. Pat. No. 2,731,066 include asphaltic compounds, coal tar products, pitch, phenol formaldehyde resins, rubber, starch, sugar, gelatin, polystyrene, methyl methacrylate or like products.
U.S. Pat. No. 4,135,029 discloses a wet-laid process for making glass fiber mats which have improved tear strength over glass mats made by the dry process. The mats include at least some randomly oriented chopped glass fibers and fiberglass strands, yarns or slivers embedded in separate layers therein. U.S. Pat. No. 4,135,029 states that commonly known bonding agents may be used to bond the fibers together, such as urea resins, phenolic resins, bone glue, polyvinyl alcohol, polyvinyl acetates and various compound and stabilizing reagents.
U.S. Pat. No. 4,178,203 relates to the manufacture of glass fiber mat products made by the wet-laid process wherein the wet fibrous web is treated with an anionic surfactant at any time after the web is prepared and before binder is applied to the mat. The resultant mat is said to have increased wet-strength.
U.S. Pat. No. 4,178,204 relates to the manufacture of glass fiber mat products made by the wet-laid process wherein a wet fibrous web is prepared that is treated with an anionic polyelectrolyte prior to binder being applied to the mat. The anionic polyelectrolytes are either soluble in water or can provide soluble dispersible salts in water, such as with an alkali metal hydroxide, ammonia or a low molecular weight organic amine. The resultant mat is said to have increased wet-strength.
U.S. Pat. No. 4,178,206 relates to the manufacture of glass fiber mat products made by the wet-laid process wherein glass fiber dispersions are prepared by mixing chopped glass fibers in water with a small amount of a select group of cationic quaternary ammonium compounds which have at least two long chain groups as part of the molecule. The resultant dispersions are said to have a relatively high glass fiber consistency.
U.S. Pat. No. 4,179,331 relates to the manufacture of glass fiber mat products made by the wet-laid process wherein glass fiber dispersions are prepared by mixing chopped glass fibers in water with a small amount of an amine oxide surfactant. The resultant dispersions are said to have a relatively high glass fiber consistency.
U.S. Pat. No. 5,407,536 relates to the manufacture of glass fiber mat products made by the wet-laid process wherein glass fiber compositions are prepared by mixing chopped glass fiber bundles in water with a small amount of an alkylamidoalkyl sultaine surfactant, which is amphoteric, to disperse the bundles into individual fibers prior to preparing the wet fibrous web. The resultant dispersions are said to have a relatively high glass fiber consistency.
U.S. Pat. No. 2,701,777 discloses asphaltic emulsions and glass mats made from the asphaltic emulsions. The asphaltic emulsions are used in the preparation of glass fiber mats. The asphaltic emulsions are made with an anionic component in the form of a fatty acid ester or mixed fatty acid esters of polyethylene glycol, the palmitic acid ester of diethylene glycol and the oleic acid ester of triethylene glycol, castor oil fatty acids of triethylene glycol and palm oil fatty acid esters of diethylene glycol.
U.S. Pat. No. 4,233,353 discloses glass fiber mats constructed from two fibrous components, including individual filaments, which provide a uniform denseness for impregnation of saturant asphalt to the mat after its formation, and extended fiber elements formed by longitudinal extension and connection of fibers from bundles of glass fibers in a wet-laid process, which furnish tear resistance. The glass fibers are bonded together with any commercially available binder, such as urea-formaldehyde or phenol-formaldehyde resins.
U.S. Pat. No. 5,744,229 discloses a glass fiber mat that contains from 68% to 90% glass fibers and from 10% to 32% binder. The binder contains from 2% to 90% polymer modified asphalt and from 10% to 98% thermosetting resin by weight of the binder. The preferred asphalt is AC grades of asphalt because they are soft and easily emulsified. The tear strength of the disclosed glass fiber mats, as shown in Table 1 of U.S. Pat. No. 5,744,229, was better than a control glass fiber mat made with a conventional binder containing SBR polymer and urea formaldehyde resin, although the tensile strength was not as good as the control.
U.S. Pat. No. 6,817,152 discloses a glass fiber mat having improved tear resistance that includes randomly oriented glass fibers, a polysiloxane compound and a formaldehyde-type binder containing a binder modifier which is a crosslinked styrene/acrylic polymer.
It is an object of the present invention to provide new and improved asphalt emulsions which allow for the economic manufacture of products made from asphalt emulsions, such as fibrous mats. It is also an object of the present invention to provide fibrous mats that are made with asphalt emulsions which allow for the preparation of fibrous mats that are strong, light weight and possess excellent tear resistance and tensile strength. It is a further object of the present invention to provide new and improved processes for manufacturing wet fibrous webs which have improved wet-strength. The processes are useful for preparing fibrous mats, such as the fiber mats of the present invention. The processes of the present invention employ an amphoteric surfactant which is applied to the wet-laid fiber web prior to the application of binder.